As the past weeks of debate over action in Syria have shown, it’s nearly impossible to discuss U.S. policy toward the Middle East without discussing Iran, and concerns over the possibility that it could obtain a nuclear weapon. Over the past three decades, the U.S. approach to the region has been, if not entirely defined by the tension between Americans and Islamic Republic, then strongly colored by it. For its part, Iran has, to a considerable extent, defined itself in opposition to the United States, the sponsor of the oppressive Shah who was overthrown in the 1979 revolution. A key foreign policy goal of the Islamic Republic is undermining and rolling back the U.S.’s influence in the neighborhood which it considers itself the natural hegemon of.

That bid for regional influence was given a generous boost by the U.S. invasion of Iraq in 2003, which removed Iran’s bitterest foe, Saddam Hussein, whose invasion of Iran in 1980 sparked the massively destructive eight-year war that killed over a million people. The United States's creation of a post-Saddam Iraqi government significantly made up of Iran’s friends and clients kicked off a years-long run of influence building that has only recently been turned back by the Arab awakening.

Brookings Institution scholar Ken Pollack, author of the new book Unthinkable: Iran, the Bomb, and American Strategy, may not have been one of the most aggressive advocates of the Iraq war, but he was arguably one of the most important. His analysis of the danger posed by Saddam Hussein in his 2002 book, The Threatening Storm: The Case for Invading Iraq, did a good deal more to bring skeptical liberals off the fence than the Strangelovean sneering of Dick Cheney or the re-heated Churchill-isms of the neocons. In the years since the Iraq war has near-universally come to be acknowledged as a mistake, Pollack’s book has been cited—i.e. blamed—by numerous pro-war liberals who came to regret their support for it.

Pollack is clearly aware of his role, or at least his perceived role, as a key liberal advocate for the invasion. “In the past, my views have been misrepresented,” he writes in the introduction to his new book. “I tried to write a balanced, nuanced book about Iraq in 2002, only to find it caricatured by people who read nothing but the subtitle—or cherry-picked lines from it.” Seeking to avoid this, Pollack posts a crystal-clear summation of the book’s argument right up front: The U.S. should try “a revamped version of the carrot-and-stick strategy,” offering Iran greater inducements in exchange for concessions on its nuclear program while also considering new forms of pressure, such as supporting “indigenous Iranian opposition groups seeking to reform or even overthrow the Islamic Republic,” to coerce those concessions. He writes that an Israeli strike on Iran “would serve no good purpose,” but that there are reasonable arguments in favor of a U.S. military strike.

“However,” Pollack concludes, “on the whole, I believe the costs and risks of containment are more acceptable than the costs and risks of starting down the path of war with Iran. I do not believe that the containment of Iran, including potentially a nuclear Iran, will be easy or painless, just preferable to the alternative.” Anticipating the criticisms of such a strategy, Pollack stresses that containment “does not mean appeasement, or even acceptance of a nuclear Iran. Containment can take many shapes, some confrontational, some far more passive. One of the keys to making containment work will be determining how assertive or reserved to be at any time.” In other words, it’s incorrect to assume that containment will be an entirely non-military approach.

The book is arranged in two parts. The first, as Pollack described to me recently, is basically “three N.I.E.’s (National Intelligence Estimates, which express the collective assessments of the U.S. intelligence community) welded together.” The first examines the Iranian leadership and how they think; the second examines the Iranian nuclear program; and the third considers the actual level of threat posed. Those seeking to analyze Iran, Pollack writes, need to familiarize themselves with two phrases: “I don’t know” and “It depends.” While this might seem at first like a cop-out, it rings quite true to anyone who’s spent a bit of time attempting to understand the opaque inner-workings of the Islamic Republic. More importantly, it expresses a kind of analytical humility that is in desperately short supply in Washington, where a pose of world-weary certainty is more common. This sense of humility underpins the entire book: There’s a lot we don’t know, but based on the best evidence we have available, here’s what I think. It strengthens Pollack’s arguments more than bold assertions of fact ever could.

Addressing the arguments against containment, Pollack makes quick work of the claim—common among anti-Iran hawks, and a favorite of Israeli Prime Minister Benjamin Netanyahu’s—that the religious ideology of Iran’s leaders would cause them to trigger a nuclear apocalypse. “Whatever Iranian leaders may believe, there is nothing they have ever done that comports with this notion, whereas much that they have done runs against it,” Pollack writes. Containing an Iran in possession of nuclear weapons will be difficult, but “the notion that they would use nuclear weapons unprovoked against the United States, Israel, or other U.S. allies in the region is not among those difficulties.”

Taking on criticisms, mainly from the left, that Obama has not done enough to demonstrate American good faith to the Iranians, Pollack de-couples the two parts of this argument. First, on the question of public messaging, he shows that the administration has tried, both through its public diplomacy (such as Obama’s Nowruz greetings, where he spoke directly to the people and the government of “the Islamic Republic of Iran”) and at the negotiating table, to demonstrate to Iran that the United States does not seek its destruction and would like to lessen tensions. In this respect, the claim that Obama has simply continued the approach of the previous administration falls on its face. The second criticism is somewhat more apt, as Pollack recognizes: The United States and its partners in the P5+1 (the permanent five members of the UN Security Council plus Germany, authorized by the United Nations with handling negotiations) have not yet offered a package of incentives that Iran’s leaders could plausibly present as a win, a necessity for any successful negotiation. We’ll have to do better, he writes, than simply offering to stop hitting Iran with more sanctions if they comply. (Having gone to press before Iranian cleric Hassan Rohani won the presidency in a surprise upset, the book understandably gives somewhat short shrift to the possibilities of a diplomatic solution, while also making clear that this is by far the preferred outcome.)

Pollack pays the military option the respect of making the strongest possible case for it, in order to show why it’s not the best option. The United States has the capacity to severely set back Iran’s nuclear work, possibly for several years through air strikes, but at enormous risk. “There are several dynamics at work that make it fairly likely that air strikes against the Iranian nuclear program would be the start of a much larger U.S.-Iranian war,” he writes, “one that could well push us into an invasion of Iran.” (italics in original.)

The second part of the book, in which Pollack lays out the argument for containment, is titled “The Strategy That Dare Not Speak Its Name.” It’s in reference to the trial of Oscar Wilde, in which the line, from a poem by Wilde’s young lover, Lord Alfred Douglas, was included in the evidence against him, leading to his conviction for gross indecency, i.e. homosexuality. It’s cheekily overstated, but it makes an important point. Even if advocates of containment obviously don’t endure half the persecution Wilde did for his sexual orientation, it’s still the case that few will openly endorse the policy for fear of being tarred as an “appeaser” of America’s enemies.

This is odd, as containment is, in fact, the strategy that the United States has been using against Iran for the last 30 years. “Containment is what Americans do when we can’t have a good relationship with a country, and we don’t want to go to war with them,” Pollack told me. “Containment is not appeasement. Quite the contrary,” he writes in the book. “The most basic way to understand a strategy of containment is that it seeks to prevent a hostile nation from causing harm to American interests and allies by ‘containing’ it within its borders until the structural flaws in its political system bring an end to the regime itself.” In contrast to the way it’s often caricatured, a strategy of containment would be aimed at demonstrating to Iran the costs of defiance. Importantly, it would keep alive the possibility of eventual U.S.-Iran rapprochement, while military strikes would almost certainly kill it for a generation or more.

And while we’re on appeasement, it’s worth considering what the dashboard saint of the hawks himself had to say about the dread word. “The word ‘appeasement’ is not popular, but appeasement has its place in all policy,” Churchill said in 1950, as the Cold War was heating up. “Make sure you put it in the right place. Appease the weak, defy the strong.” Later he said that, “appeasement from strength is magnanimous and noble and might be the surest and perhaps the only path to world peace.” This is something to keep in mind when Winston is trotted out, as he surely will be, to oppose any nuclear deal, whatever its contours.

In this book, Pollack makes repeatedly clear that the United States is acting from a place of enormous strength vis a vis Iran. While the calls for military action against Iran seem to arise every few months here in Washington, and will undoubtedly do so again soon—even as Iran has undertaken the most serious and sustained diplomatic outreach effort in its history—Pollack has provided a useful briefing for anyone seeking to better understand what drives Iranian policy. Even more, he tackles the nature of the challenge the country poses to the United States. The book proves a valuable tool for pushing back on claims that containment is just a policy of surrender. In making the case here that containment is the worst possible strategy, except for all the others, Pollack has contributed to a smarter, more reality-based Iran policy debate.